Reset GL_PACK_ROW_LENGTH to 0 before calls to glReadPixels.

The client side of the command buffer handles emulation of the
GL_PACK_ROW_LENGTH parameter.

TEST=conformance2/reading/read-pixels-pack-parameters.html

BUG=602688

Change-Id: Id3415d56c565504b423f2a32d91d865274667037
Reviewed-on: https://chromium-review.googlesource.com/567430
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486005}

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -201,8 +201,6 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
     self.Skip('conformance2/textures/misc/' +
         'copy-texture-image-webgl-specific.html',
         ['win', 'passthrough', 'd3d11'], bug=602688)
-    self.Skip('conformance2/reading/read-pixels-pack-parameters.html',
-        ['win', 'passthrough', 'd3d11'], bug=602688)
     self.Skip('conformance2/reading/read-pixels-into-pixel-pack-buffer.html',
         ['win', 'passthrough', 'd3d11'], bug=602688)
 

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc

@@ -250,6 +250,27 @@ class ScopedUnpackStateButAlignmentReset {
   GLint image_height_ = 0;
 };
 
+class ScopedPackStateRowLengthReset {
+ public:
+  ScopedPackStateRowLengthReset(bool enable) {
+    if (!enable) {
+      return;
+    }
+
+    glGetIntegerv(GL_PACK_ROW_LENGTH, &row_length_);
+    glPixelStorei(GL_PACK_ROW_LENGTH, 0);
+  }
+
+  ~ScopedPackStateRowLengthReset() {
+    if (row_length_ != 0) {
+      glPixelStorei(GL_PACK_ROW_LENGTH, row_length_);
+    }
+  }
+
+ private:
+  GLint row_length_ = 0;
+};
+
 }  // anonymous namespace
 
 // Implementations of commands
@@ -1757,6 +1778,8 @@ error::Error GLES2DecoderPassthroughImpl::DoReadPixels(GLint x,
                                                        void* pixels,
                                                        int32_t* success) {
   FlushErrors();
+  ScopedPackStateRowLengthReset reset_row_length(
+      bufsize != 0 && feature_info_->gl_version_info().is_es3);
   glReadPixelsRobustANGLE(x, y, width, height, format, type, bufsize, length,
                           columns, rows, pixels);
   *success = FlushErrors() ? 0 : 1;